- OpExtInstImport now enforces correct instruction set
- OpExtInst dispatch done
- Implemented FAbs, SAbs

Bug: b/127804400
Change-Id: I41b9755afeeb9a61c8294beb610f5e6c77080fa5
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/26408Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Chris Forbes <chrisforbes@google.com>
Presubmit-Ready: Chris Forbes <chrisforbes@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>